Linköping University

About: Linköping University is a education organization based out in Linköping, Sweden. It is known for research contribution in the topics: Population & Thin film. The organization has 15671 authors who have published 50013 publications receiving 1542189 citations.

Massive MIMO in Real Propagation Environments: Do All Antennas Contribute Equally?

Abstract: Massive MIMO can greatly increase both spectral and transmit-energy efficiency. This is achieved by allowing the number of antennas and RF chains to grow very large. However, the challenges include high system complexity and hardware energy consumption. Here we investigate the possibilities to reduce the required number of RF chains, by performing antenna selection. While this approach is not a very effective strategy for theoretical independent Rayleigh fading channels, a substantial reduction in the number of RF chains can be achieved for real massive MIMO channels, without significant performance loss. We evaluate antenna selection performance on measured channels at 2.6 GHz, using a linear and a cylindrical array, both having 128 elements. Sum-rate maximization is used as the criterion for antenna selection. A selection scheme based on convex optimization is nearly optimal and used as a benchmark. The achieved sum-rate is compared with that of a very simple scheme that selects the antennas with the highest received power. The power-based scheme gives performance close to the convex optimization scheme, for the measured channels. This observation indicates a potential for significant reductions of massive MIMO implementation complexity, by reducing the number of RF chains and performing antenna selection using simple algorithms.

Immunology of Preeclampsia

Abstract: Preeclampsia is a placenta-dependent disorder with both local and systemic anomalies with neonatal and maternal morbidity. It is manifested late in pregnancy, but the onset is during early stages of

Solutions Offerings: A Critical Review and Reconceptualisation

Abstract: Purpose– The purpose of this paper is to offer a critical analysis of the literature of solutions offerings; to provide a new conceptual framework, incorporating dimensions that can distinguish between different kinds of solutions and connect their different characteristics.Design/methodology/approach– The paper takes a critical review of the relevant literature, 28 contributions being identified in a search of three major databases and a range of other published work for the broader perspective, illustrated by real‐world examples.Findings– There is no unanimous and rigorous definition of solutions, but rather a number of often broad and generic descriptions that could be applied to a wide array of different offerings, if not generically.Research limitations/implications– The sample of subject‐specific contributions to the literature may not have been sufficient, and a wider selection of keywords to identify them might have captured a richer variety of concepts and opinions.Originality/value– This structured and critical review contributes to the literature on services and solutions, by developing a conceptual framework as a basis for future studies and current management strategy.

Augmented increase in tight junction permeability by luminal stimuli in the non-inflamed ileum of Crohn's disease

Abstract: Background: Crohn9s disease is associated with deranged intestinal permeability in vivo, suggesting dysfunction of tight junctions. The luminal contents are important for development of neoinflammation following resection. Regulation of tight junctions by luminal factors has not previously been studied in Crohn9s disease. Aims: The aim of the study was to investigate the effects of a luminal stimulus, known to affect tight junctions, on the distal ileum in patients with Crohn9s disease. Patients: Surgical specimens from the distal ileum of patients with Crohn9s disease (n=12) were studied, and ileal specimens from colon cancer patients (n=13) served as controls. Methods: Mucosal permeability to 51 Cr-EDTA and electrical resistance were studied in Ussing chambers during luminal exposure to sodium caprate (a constituent of milk fat, affecting tight junctions) or to buffer only. The mechanisms involved were studied by mucosal ATP levels, and by electron and confocal microscopy. Results: Baseline permeability was the same in non-inflamed ileum of Crohn9s disease and controls. Sodium caprate induced a rapid increase in paracellular permeability—that is, increased permeation of 51 Cr-EDTA and decreased electrical resistance—which was more pronounced in non-inflamed ileum of Crohn9s disease, and electron microscopy showed dilatations within the tight junctions. Moreover, sodium caprate induced disassembly of perijunctional filamentous actin was more pronounced in Crohn9s disease mucosa. Mucosal permeability changes were accompanied by mitochondrial swelling and a fall in epithelial ATP content, suggesting uncoupling of oxidative phosphorylation. Conclusions: The tight junctions in the non-inflamed distal ileum of Crohn9s disease were more reactive to luminal stimuli, possibly mediated via disturbed cytoskeletal contractility. This could contribute to the development of mucosal neoinflammation in Crohn9s disease.